DESCRIPTION: (Applicant's Abstract) The goal of the proposed project is to develop a battery of tests (PD Battery) that could provide an inexpensive and objective aid for, first, the early diagnosis of Parkinson's syndrome (PS) and second, to aid in its differential diagnosis, such as idiopathic Parkinson's disease (iPD); Parkinson-Plus syndromes (P-Plus) such as striato-nigral degeneration; and essential tremor (ET) as distinguished from tremor predominant parkinsonism and others. The PD Battery has been developed that, in preliminary studies, clearly distinguishes between normal control (NC) subjects and patients with early mild presumptive iPD (95 percent sensitivity, 94 percent specificity and the area under the receiver-operator curve [ROC] of 0.98). The battery incorporates tests of motor function, olfaction, and affective state (i.e., depression). When additional NC subjects and iPD patients were studied in a prospective manner, the test battery correctly identified 44 of 48 NC subjects and 10 of the 11 iPD patients. In addition, 7 of 9 patients with ET had test results in the normal range suggesting that the battery can aid in the differentiation of tremor predominant iPD and ET. The next step is to validate the PD Battery by prospectively testing patients in whom PS is suspected but the diagnosis is uncertain (the Uncertain PS group). These patients will undergo the PD Battery, Unified Parkinson Disease Rating Scale (UPDRS) upon entrance into the study. Two years later, a MRI scan and the UPDRS and motor testing before and after levodopa administration will be done. These tests should identify which of these patients become probably normal, probably iPD or Probable P-Plus. Results of these evaluations will be correlated with their results from the PD Battery at time of entrance into the study. To further validate the battery, more NC subjects and patients with: 1) newly diagnosed and mildly affected PS; 2) P-Plus syndromes; 3) ET; 4) mild Alzheimer's disease (AD) and 5) AD with parkinsonian features (AD/PD) will be tested. If successful, the PD Battery could help assure appropriate patients receive appropriate care, thus, minimizing health costs and disability. In the future, the PD Battery could allow early or pre-clinical detection of persons at risk. this battery for early detection, coupled with future neuro-protective therapies, could further reduce health costs and disability. In addition , the test battery could be used in the future to aid research into the possible genetic and/or environmental causes of iPD.